Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Homocysteine is a sulphur-containing amino acid that is derived primarily from protein of animal origin. Classical homocystinuria is an inherited metabolic disorder that arises from defects in either the re-methylation or trans-sulphuration pathways of homocysteine metabolism and leads to skeletal abnormalities, mental retardation and a high risk of vascular disease. In contrast, moderate hyperhomocysteinaemia is associated with an increased risk of both arterial and venous thrombotic disease but no other abnormalities. This increased risk appears to be independent of other conventional risk factors. Many cases of hyperhomocysteineaemia have been attributed to defects in the enzyme cystathionine-beta-synthase (CBS) but this accounts for less than 1.5% of cases. A thermolabile variant of the enzyme methylenetetrahydrofolate reductase (MTHFR) arises from a C --> T transition at nucleotide 677 in the MTHFR gene resulting in an alanine-to-valine substitution. While the mutation does not appear to be associated with an increased risk of vascular disease, it results in excessively high homocysteine levels in response to a low or low-normal serum folate. Supplementation of the diet with folate, B6 and B12 can reduce homocysteine levels and this is the mainstay of treatment. Supplementation of grain with folate is undertaken in the USA to reduce the risk of neural tube defects in pregnant women. However, by reducing plasma homocysteine levels, it is estimated that this will save up to 50,000 lives per annum.
Baillieres Best Pract Res Clin Haematol 1999 Sep
PMID:Hyperhomocysteinaemia. 1085 81

Osteoporosis screening of adults ages 40 to 60 who attended community-based adult training centers was conducted utilizing dual-energy X-ray absorptiometry (DEXA) measurements of the calcaneus. Valid measurements were obtained on 107 individuals, a response rate of 94%. One fifth of the sample (21%) had osteoporosis and 34% had osteopenia. On multiple regression analysis, the most significant predictors of BMD were Down syndrome, mobility status, and race. Future studies involving larger samples of middle-age adults with mental retardation/developmental disabilities will clarify the need and optimum age for osteoporosis screening.
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PMID:Screening for osteoporosis in community-dwelling adults with mental retardation. 1098 Nov 93

North Carolina has developed coordinated care systems for people dually diagnosed with both a mental retardation and a different major mental illness. In response to a class action lawsuit, the state has become a leader in treatment of this form of dual diagnosis. Systems of care for this "Thomas S class" operate in each of 41 area programs for mental health, developmental disabilities, and substance abuse. Networks of care among leaders in mental health and developmental disability promote the coordination of health, housing, social, and vocational services. A survey of 100 area program leaders finds extensive cooperation and a variety of services provided and contracted for, both within and beyond each area program, particularly among developmental disability specialists. Cooperation among leaders is associated with service variety and inter-organizational linkages. The extent of relationships among provider organizations is associated with better access to care. Best practice includes a single portal of entry and inter-agency councils.
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PMID:New patterns of community care: coordinated services for dually diagnosed adults in North Carolina. 1126 5

Duchenne/Becker muscular dystrophy (DMD/BMD) are the most common inherited muscular diseases caused by mutations in the dystrophin gene. The identification of novel dystrophins in the brain has recently implicated its absence or malfunction etiologically in mental retardation (MR). We therefore examined the relationship between molecular abnormalities and clinical phenotypes. Deletions of the dystrophin gene were analyzed in a total of 137 DMD/BMD patients (DMD 94, BMD 43) to determine central nervous system (CNS) symptoms. The mental capacity was assessed and patients with IQs below 70 were defined as mentally retarded. Thirty-nine percent of DMD boys and 12% of BMD patients were classified as mentally retarded. Eight DMD and 2 BMD patients were diagnosed as having autism. Forty-four percent of DMD and 79% of BMD patients had deletions in the dystrophin gene. All the DMD/BMD patients with deletions upstream of the 5' end of the gene were mentally normal. All of DMD/BMD patients with MR and/or autism had deletions containing the 3' end, although some patients with similar deletions were mentally normal. Our data suggest that Dp140, Dp71 and/or Dp116, the C-terminal translational products of dystrophin, may be related to MR and/or autism in DMD/BMD. However, there was an exception in our series. Three of eight sibling pairs in our cases had different phenotypes, although they had the same mutations in the dystrophin gene. Thus the CNS phenotypes were not determined by the mutations of dystrophin gene alone, and the interaction of dystrophin with other nuclear genes may play important roles.
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PMID:[Central nervous system involvements in Duchenne/Becker muscular dystrophy]. 1172 14

Newborn screening for congenital hypothyroidism (CH), is one of the major achievements of medicine because early diagnosis and treatment has resulted in normal development in the vast majority of cases. However, all studies on outcome report up to 10% of patients with residual problems regarding mental development and neurological symptoms despite early diagnosis. Factors clearly associated with a less favourable outcome are late onset and an inadequate dosage of thyroid hormone substitution, a poor social-economic environment and compliance problems, while the impact of severity of CH at diagnosis on outcome is not completely settled, although most studies demonstrate a correlation between severity of hypothyroidism and poorer outcome. More recently in a few cases the molecular basis of CH has been clarified. It has become evident that, in some patients with persistent mental retardation and neurological symptoms, defects in transcription factors which are expressed in the thyroid gland as well as in the central nervous system (CNS) during embryonic development cause both defective thyroid and CNS development. The clarification of further molecular defects which affect the thyroid gland and brain development will help us to understand the poor outcome of patients with CH in the era of newborn screening and these diagnostic advances will ensure adequate counselling and care for these patients.
Best Pract Res Clin Endocrinol Metab 2002 Jun
PMID:Long-term consequences of congenital hypothyroidism in the era of screening programmes. 1206 98

Sudden unexpected death in epilepsy (SUDEP) accounts for approximately 2% of deaths in population-based cohorts of epilepsy, and up to 25% of deaths in cohorts of more severe epilepsy. When it occurs, SUDEP usually follows a generalised tonic-clonic seizure. Unresponsiveness, apnoea, and cardiac arrest occur in SUDEP, rather than the typical gradual recovery. The great majority of tonic-clonic seizures occur without difficulty and how the rare seizure associated with SUDEP differs from others is unknown.Three mechanisms have been proposed for SUDEP: cardiac arrhythmia, neurogenic pulmonary oedema, and postictal suppression of brainstem respiratory centres leading to central apnoea. Recent studies have found that the incidence of SUDEP increases with the severity of epilepsy in the population studied. The duration of epilepsy, number of tonic-clonic seizures, mental retardation, and simultaneous treatment with more than two antiepileptic drugs are independent risk factors for SUDEP. Some studies have reported that carbamazepine use, carbamazepine toxicity, and frequent, rapid changes in carbamazepine levels, may be associated with SUDEP. Other evidence indicates that carbamazepine could potentially increase the risk for SUDEP by causing arrhythmia or by altering cardiac autonomic function. However, this evidence is tenuous and most studies have not found an association between the use of carbamazepine or any other individual antiepileptic drug and SUDEP. There is little information regarding antiepileptic drugs other than phenytoin and carbamazepine. The incidence of SUDEP with gabapentin, tiagabine, and lamotrigine clinical development programmes is in the range found in other populations with refractory epilepsy. This suggests that these individual antiepileptic drugs are no more likely to cause SUDEP than antiepileptic drugs in general. Best current evidence indicates that the risk of SUDEP can be decreased by aggressive treatment of tonic-clonic seizures with as few antiepileptic drugs as necessary to achieve complete control. At present there is no strong reason to avoid any particular antiepileptic drug. Further studies are needed to elucidate the potential role of individual antiepileptic drugs in SUDEP and establish clinical relevance, if any. These studies may be challenging to conduct and interpret because SUDEP is relatively uncommon and large numbers will be necessary to narrow confidence intervals to determine the clinical relevance. Also adjustments will be needed to account for the potent risks associated with other independent factors.
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PMID:Do antiepileptic drugs play a role in sudden unexpected death in epilepsy? 1286 2

Analyses of deletions in the dystrophin gene and of cognitive status were performed on patients with Duchenne (DMD) or Becker (BMD) muscular dystrophy in order to find a correlation between both features. Molecular study by multiplex and simplex PCR of dystrophin exons led to the identification of 51 deletions in 126 unrelated patients. Most of them were frameshift, in full agreement with severe clinical symptoms, three patients with a BMD-like phenotype had in-frame mutations. Deletions were localized with reference to the different dystrophin isoform sequences and were clustered in two main areas, 5' and central+ 3' end of the gene. Cognitive abilities were tested in 47 out of 51 patients with identified mutations, 23 of them being mentally impaired. Comparison of molecular and neuropsychological features showed that deletions localized in central and 3' parts of the gene (18 out of 23) are preferentially associated with mental impairment. Fourteen of them were found in the regulatory and coding sequences for the three CNS specific carboxy terminal isoforms. Therefore, though mutations with variable locations may lead to cognitive impairment, our results show that deletions in the distal portion of the gene are basically related to mental retardation.
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PMID:Dystrophin deletions and cognitive impairment in Duchenne/Becker muscular dystrophy. 1497 63

The study of neurogenetic microdeletion syndromes provides an insight into the developmental psychopathology of psychiatric disorders. The aim of the study was to evaluate the prevalence of psychiatric disorders, especially obsessive-compulsive disorder (OCD), in patients with velocardiofacial syndrome (VCFS), a 22q11 microdeletion syndrome. Forty-three subjects with VCFS of mean age 18.3 +/- 10.6 years were comprehensively assessed using semi-structured psychiatric interview and the Yale-Brown obsessive compulsive scale (Y-BOCS). Best estimate diagnoses were made on the basis of information gathered from subjects, parents, teachers, and social workers. Fourteen VCFS subjects (32.6%) met the DSM-IV criteria for OCD. OCD had an early age of onset and generally responded to fluoxetine treatment. It was not related to mental retardation. The most common obsessive-compulsive symptoms were contamination, aggression, somatic worries, hoarding, repetitive questions, and cleaning. Sixteen of the 43 patients (37.2%) had attention-deficit/hyperactivity disorder (ADHD), and 7 (16.2%) had psychotic disorder. The results of our study suggest that there is a strong association between VCFS and early-onset OCD. This finding may be significant in the understanding of the underlying genetic basis of OCD.
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PMID:Obsessive-compulsive disorder in patients with velocardiofacial (22q11 deletion) syndrome. 1504 57

Genomic copy-number variations (CNVs) involving large DNA segments are known to cause many genetic disorders. Depending on the changes, they are predicted to lead either to decreased or an increased gene expression. However, the ability to detect smaller exonic copy-number changes has not been explored. Here we describe a new oligonucleotide-based comparative genomic hybridization (CGH)-array approach for high-throughput detection of exonic deletions or duplications and its application to deletion/duplication analyses of the genes encoding CFTR, six sarcoglycans (SGCA, SGCB, SGCG, SGCD, SGCE, and SGCZ), and DMD. In this work we show the successful development of an array format containing 158 exons that collectively span eight genes and its clinical application for the rapid screening of deletions and duplications in a diagnostic setting. We have analyzed a series of 35 DNA samples from patients affected with cystic fibrosis (CF), Duchenne and Becker muscular dystrophies (DMD/BMD), or sarcoglycanopathies, and have characterized exonic copy-number changes that have been validated with other methods. Interestingly, even heterozygous deletions and duplications of only one exon, as well as mosaic deletions, were detected by this CGH approach. Our results showed that the resolution is very high, as abnormalities of about 1.5-2 kb could be detected. Since this approach is completely scalable, this new molecular tool will allow the screening of combinations of genes involved in a particular group of clinically and genetically heterogeneous disorders such as mental retardation, muscular dystrophies and brain malformations.
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PMID:Detection of exonic copy-number changes using a highly efficient oligonucleotide-based comparative genomic hybridization-array method. 1875 6

While the function of dystrophin in muscle disease has been thoroughly investigated, dystrophin and associated proteins also have important roles in the central nervous system. Many patients with Duchenne and Becker muscular dystrophies (D/BMD) have cognitive impairment, learning disability, and an increased incidence of some neuropsychiatric disorders. Accordingly, dystrophin and members of the dystrophin-associated glycoprotein complex (DGC) are found in the brain where they participate in macromolecular assemblies that anchor receptors to specialized sites within the membrane. In neurons, dystrophin and the DGC participate in the postsynaptic clustering and stabilization of some inhibitory GABAergic synapses. During development, alpha-dystroglycan functions as an extracellular matrix receptor controlling, amongst other things, neuronal migration in the developing cortex and cerebellum. Several types of congenital muscular dystrophy caused by impaired alpha-dystroglycan glycosylation cause neuronal migration abnormalities and mental retardation. In glial cells, the DGC is involved in the organization of protein complexes that target water-channels to the plasma membrane. Finally, mutations in the gene encoding epsilon-sarcoglycan cause the neurogenic movement disorder, myoclonus-dystonia syndrome implicating epsilon-sarcoglycan in dopaminergic neurotransmission. In this review we describe the recent progress in defining the role of the DGC and associated proteins in the brain.
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PMID:The neurobiology of the dystrophin-associated glycoprotein complex. 1917 27


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